1. Field of the Invention
The field of the invention is that of driver elements in self-reversing tapping attachments, which are tools that carry taps for threading holes and are driven by an external drive source such as a driving machine, drive being imparted from a movable body in the tapping attachment body to a member carrying the tap and the tapping attachment including means for reversing the rotation of the tap.
2. Description of the Prior Art
Related patents to the same inventor as named on the application herein are U.S. Pat. Nos. 3,397,588; 3,472,347; 3,717,892; 3,946,844; 3,999,642; 4,014,421; 4,029,429; 4,067,424; and 5,011,344. The above-cited patents relate, among other things, to clutching arrangements in tapping attachments, both for direct drive and for reverse drive.
Existing tapping attachments are many and varied, and constitute a relatively mature art. Within the relatively recent past, however, there has arisen a need for improvements in tapping attachments due to the advent of high speed tapping that is, tapping at high rpm. A need for improvement in tapping attachments for high speed application is particularly pronounced with respect to self-reversing tapping attachments, i.e., tapping attachments which provide for a reverse rotation of the tap in order to aid its withdrawal from a hole which has been threaded by it.
A common device for imparting drive to a drive member of a tapping attachment in existing devices is the ball drive. In a ball drive, a driver member impacts with driver balls held in or associated with a driving element which in turn impacts with a dog or like member for the purpose of imparting drive, either forward or reverse, to a tap holder in the form of a spindle.
In existing ball drive arrangements, particularly in high speed applications, impacts between the balls and the various dogs and splines with which they engage for the purpose of imparting drive, result in shock and vibration, together with substantial wear of the machine elements.
The need for drive elements of tapping attachments able to withstand high performance conditions is particularly pronounced in regard to Computer Numeric Control (CNC) applications. Under CNC operation, time is particularly of the essence for withdrawing a tap from a hole which it has threaded in that the CNC operation provides for a computer controlled transfer of driving force from one tap attachment to another, timely removal of a previously used tap from a hole being critical in such an operation.
Therefore, there has been a felt but unfulfilled need for a driving arrangement in a tapping attachment whereby in a ball drive, shock and wear within the driving and clutching elements are minimized, in particular for high speed applications.